Circuit breaker



1948. o. 5. JENNINGS I 2,447,652

cmcurr BREAKER Filed Oct. 30, 1942 2 Sheets-Sheet l Insu/a Insv/af/bnWITNESSES: INVENTOR O/A er \ijrm/hys, 1

Aug. 24, 1948. o. 5. JENNINGS 2,447,652

cmcun' BREAKER Filed Oct. 30, 1942 2 Sheets-Sheet 2 WITNESSES: INVEN'fOR5/. 4 j/ Oliver 5: Jam/wh s.

{ a/MW Patented Aug. 24, 1948 CIRCUIT BREAKER Oliver 8. Jennings,Pittsburgh, Pa minor to Westinghouse Electric'Corpor-ation, EastPittsburgh, Pm, a corporation of Pennsylvania Application October 30,1942, Serial No. 463,933

8 Claims. 1

The invention relates to circuit breakers and more particularly toautomatic circuit breakers having current responsive tripping means forautomatically tripping the breaker in response to predetermined overloadcurrent conditions.

An object or the invention is the provision 01' a circuit breaker withan improved trip device of simple construction which is operable to tripthe breaker instantaneousl upon the occurrence of heavy overloads abovea predetermined magnitude or on short circuits, and which is operable totrip the breaker after a time delay in response to overloads of lessermagnitude.

Another object of the invention is the provision of a circuit breakerwith a trip device having a current responsive bimetallic trip elementand a current responsive magnetic tripping means operable independentlyunder some conditions to trip the breaker, the two being arranged in a,novel manner to at times mutually assist in ellecting tripping of thebreaker.

Another object of the invention is the provision of a circuit breaker asdescribed in the preceding objects, wherein the parts are so arrangedthat substantially no undesirable stresses are applied to the bimetaltrip element by the magnetic means.

Another object of the invention is the provision of a circuit breakerwith an improved thermalmagnetic trip device wherein the flow of currentthrough the bimetal element energizes the magnetic tripping means sothat no separate energizing coil is required for the magnetic means.

Another object of the invention is the provision of a circuit breakerwith an improved trip device having parts novelly arranged so that onlya relatively light tripping force by the electroresponsive trippingmeans is required to trip the breaker mechanism.

1 Another object of the invention is the provision of a circuit breakerwith an improved tripping mechanism comprising a rotatable latch memberhaving a segmental or arcuate latch portion disposed ,very close to theaxis of rotation of the latch and wherein the tripping forces producedby the bimetal element and the magnetic means are applied to the latchmember at points relatively distant from the axis of rotation of thelatch and on opposite sides of the axis.

Another object of the invention is the'provision of a circuit breakerhaving a, rotatable latch with the latch point close to the axis ofrotation of the latch, and wherein a motion amplifier is interposedbetween the latch and the bimetal trip element to amplify the movementof the bimetal element, the parts being arranged to obtain a largemechanical advantage in a small space.

Another object of the invention is the provision of a circuit breakerwith an improved current energized magnetic tripping means wherein themagnetic means acts directly on the circuit breaker latch with a largemechanical advantage and yet the air gap of the magnetic means ismaintained small.

Another object of the invention is the provision of an improved circuitbreaker construction that is very simple and compact, reliable inoperation and economical to manufacture.

The above and other objects and advantages of the invention, togetherwith the construction and mode of operation thereof, will be bestunderstood from the folowing detailed description of a preferredembodiment of the invention when read in conjunction with theaccompanying drawings in which Figure 1 is a. side view, partly insection, of a circuit breaker embodying the invention. with the sideplate of the casing removed to show the mechanism and other part, thecircuit breaker mechanism being shown in the closed circuit position,

Fig. 2 is a view similar to Fig. l but showing the circuit breaker theinstant it has been tripped by operation of the magnetic tripping means,

Fig. 3 is a fragmentary view illustrating the tripping of the breaker inresponse to operation of the bimetallic trip element,

Fig. 4 is a detail sectional view of the magnetic means .takensubstantially along the section IVIV oi Fig. l, and i Fig. 5 is a detailsectional view of the latching means taken substantially on the line V-Vof Fig. 1.

Referring to the drawings, the circuit breaker comprises in general acasing I of molded insulating material, a pair of terminal conductors 9,and ll.mounted on the casing adjacent the opposite ends thereof, astationary contact IS, a cooperating movable contact IS, an areextinguisher l1, operating mechanism indicated generally at IQ foropening and closing the contacts, and a trip device indicated generallyat 2! cooperating with the operating mechanism for causing automaticopening operation of the contacts in response to predetermined overloadconditions.

The casing 1 is open at one side and is provided with various recessesand surfaces for removably receiving and supporting the parts of thecircuit breaker so that pp metal mounting frame or br being directlysupported by the molded mate'- ylal of the casing. A side cover plate28, not

shown in Figs. 1, 2 and 3 but a part of which is shown in Figs. 4 and 5.is adapted to be removably mounted on the open side of the casingsection1 to complete the casing and retain the parts in mounted position. Theside plate is secured on the casing by bolts (not shown) which extendthrough openings 25 in the casing and side plate.

The side plate is also provided with recesses and surfaces forsupporting the parts of the circuit breaker;

The construction of the upper terminal conductor 9. contacts lI-IU, arcextinguisher i1, operating mechanism It (except for the trip device),and the mounting arrangement of these parts in the casing aresubstantially similar to the corresponding parts of the circuit breakerrequired, all of the parts disclosed in my Patent No. 2,429,722, datedOctober 28. 1947, and assigned to the assignee of'the present invention.

The upper terminal conductor 9 is mounted in a slot provided therefor inthe casing section I and the upper end of the conductor extends out-.wardly into a niche formed in this end of the casing. A terminal screwis threadedly mounted in the outer end of the terminal conductor formaking connection to an external circuit. The

stationary contact if is secured to the inner end of the terminalconductor 0 within the casing. The are extinguishing device Hcomprises-a pair of U-shaped magnetic elements 21 disposed in a fiberare chute 29 partially surrounding the path of the are drawn by themovable contact .upon interruption of the circuit. 1 The operatingmechanism for operating the movable contact to open and closed circuitposition. comprises a bifurcated switch arm ii to the inner end of whichthe movable contact I! is secured, a yoke-shaped releasable carrier,lever sists of a generally flat lever and is pivotally mounted withinthe casing 1 adjacent the side outer end thereof and projects laterallyfrom the lever. The projecting end of the stud Ii carries a roller (notshown) which is adapted to bear against and roll on the inner surface ofthe side plate 23 of the casing. The operating lever thus hastwo spacedbearings for its pivotal movement.

The overcenter spring I! is disposed between the legs or the bifurcatedportion of the switch arm II and is movable in the space between thespaced legs of the carrier lever 31. One end of the spring is connectedto an intermediate point of the switch arm 3i and the other end of thespring is hooked over a circular slot in the central portion of the studIi on the operating lever II for pivotally supporting the switch arm II,a

manually operable operating lever 38. and an vovercenter operatingspring 31 which is connected in tension between the switch arm 3! and va part of the operating lever 85;

The releasable carrier lever "which is of conducting material has spacedlegs rigidly connected by an integral cross member and joined at theirlower ends by alatch element 38 which cooperates with a movable latch-ofthe trip device. The latch element is secured between the lower ends ofthe legs of the carrier member by means of rivets 4|. The legs of thecarrier lever are generally V-shaped in side elevation, and the switcharm Ii is pivotally supported in the apex of the carrier. lever formovement back and forth to open and closed circuit positions in the V-shaped notches formed by the legs of the carrier. The switch arm II isbifurcated to form spaced legs which are notched at their outer ends forpivotally engaging the legs .of the carrier lever 83 at the apexthereof. The carrier lever a is mounted for pivotal movement by a pivotpin 43, the ends of which are supported in cylindrical bearing recessesprovided therefor in the 36. The spring 3 serves to retain the switcharm in pivotal engagement with the carrier lever II and the operatinglever in pivotal engagement with its bearings. The spring also functionsto actuate the switch arm to open and closed position with a snap actionupon movement of the operating lever to oil and on positions, and

provides the'required contact pressure in the closed circuit position ofthe breaker.

The operating lever 35 is moved upwardly to the on" position shown inFig. l to effect closing'of the circuit breaker. As soon as the line ofaction of the spring I! is moved above the pivot .axis n of the switcharm II the spring acts to move the switch-farm to closed circuitposition with a snap action. To manually open the contacts of thecircult breaker the operating lever is moved downwardly to the "oposition. and as soon as the line of action of the spring 31 passesbelow the pivot axis 53, the spring acts to move the switch arm to-opencircuit position with a snap action. In the manually opened position ofthe switch arm ii the switch arm bears against the lower edges of thev-shaped notches formed in the legs of the carrier lever 33, these-edgesacting as open position stops upon manually opening the circuit breaker.

The circuit breaker is adapted to be automatically opened in response topredetermined overshown in Fig. 1 by the latch of the trip device whichengages the tip of the latch element 30. The manually operable operatinglever 35 conload conditions by operation of the trip device II whichwill be hereinafter described. The operation of the trip device effectsrelease of the releasable carrier lever 33 whereupon the overcenterspring 31 moves the carrier lever in a counterclockwise or upwarddirection about its pivot 43, thereby shifting the pivot axis 53 of theswitch arm above the line of action of the spring 31, thus causing snapacting movement of the switch arm to the open circuit position shown inFig. 2. This circuit opening movement of the switch arm will take placeirrespective oi the position of the operating handle even though theoperating handle were held in closed position. Thus the switch arm istrip-free of the operating lever. During automatic opening operation ofthe circuit breaker, the operating spring. also acts to move theoperating lever I! to an intermediate indicating position as shown in m.2, the lever being stopped in this intermediate indicating position bythe engagement of a resetting projection 55 on the operating lever withan upper edge of a releasable carrier lever 39.

Before the breaker can be manually reclosed following a trippingoperation, it is necessary to reset the releasable carrier lever 33 backto its normal latched position. This is accomplished by moving theoperating lever downwardly to the of! position. During this movement theresetting projection 55 moves the carrier lever in a clockwise directionabout the pivot 93 back to its normal latched position where it isreengaged by the latch of the trip device. The circuit breaker may bemanually closed following resetting thereof by moving the handleupwardly to the on" position in the previously described manner.

The trip device 2i is removably mounted in the lower part of the circuitbreaker casing and comprises a rotatably mounted latch member 51controlled by an electromagnet 59 and by a current responsive bimetalelement 91, each of which is operable to move the latch member toreleased position.

The latch member comprises a generally cylindrical member 51 havingflattened portions on opposite sides thereof. A notch or slot 58 (Fig.5) is cut out of thecentral portion of the latch mem-' beer for adistance slightly past the axis of rotation of the latch member, leavingan arcuate or segmental latch portion 90, the arcuate edge of which isadapted to engage and latch the releasable carrier lever 33 in thenormal position shown in Fig. 1. The latch member 51 is rotatablymounted by pivot studs 53 which project from the opposite ends of thelatch member and engage in circular bearing recesses provided in thecasing 1 and side plate 23 of the casing. The axis of rotation orturning movement 01'. the latch member 51 passes substantially throughthe center thereof;

By this construction the arcuate latch surface of the latch isconcentric with and located very close to the axis of rotation of thelatch member. A lever 95 is secured intermediate its ends by rivets 61to one of the flattened sides of the latch member 51, the lever 95providing oppositely projecting lever arms on either side of the axis ofrotation of the latch member. The latch member is biased to the latchingposition shown in Fig. l by means of a spring 69 which is mounted on astud 1| secured in the side wall of the casing 1. One end of the springengages in an opening of an ear formed in one arm of the latch lever 69.The spring is coiled about the stud 1| and the other end of the springis settable. in any one of a plurality of openings 13 formed in the sidewall of the casing 1. These openings 13 provide means for adjusting theforce 01' the spring to adjust the instantaneous trip setting of thecircuit breaker.

The magnetic tripping means 59 comprises a magnetic armature secured toone arm of the latch lever 65, and a cooperating U-shaped magnet ormagnetic member 11 which is fixedly mounted in supporting recesses inthe casing adjacent the armature 15 in a position to provide an air gapbetween the armature and the U-shaped magnet. The armature 15 isprovided with a projecting rib 19 (Fig. 4) which projects partly intothe space between the legs of the magnet 11. This rib 19 provides for arelatively small air gap despite the relatively long travel movement ofthe armature between its unattracted and attracted position, therelatively long movement being necessary due to the fact that the latchsurface or the latch is located very close to the axis of rotation ofthe latch member 51. The

stationary magnet 11 is set at a slight angle to permit the armature tomove squarely against the pole faces of the magnet as the armature turnsabout the rotatable axis 99. The magnetic means is energized in responseto the current of the circuit controlled by the breaker and theconstruc- \ion is such that the armature will be moved to attractedposition to release the latch and trip the circuit breaker instantlyupon the occurrence of an overload above a predetermined magnitude, forexample, in excess of eight or ten times the rated current of thebreaker, and on short circuits.

The current responsive birnetal element ll comprises a strip ofbimetallic material which is secured at its inner end to the inner endor the terminal conductor II. A portion of the bimetallic strip 9!passes through the space between the leg, of the U-shaped magnet 11 sothat the flow of current through the bimetal element serves to energizeand produce the magnetic flux in the magnet 11 and armature 15. Thisportion of the bimetal strip and a portion of the conductor areinsulated from the magnet 11 by a layer of insulation 19. The bimetallicstrip 9| extends generally parallel to the latch lever I and the outerand of the bimetallic strip is disposed opposite the end of one leverarm of the latch lever 65. A flexible conductor 9! electrically connectsthe free outer end of the bimetallic strip 9| to the releasable carrierlever 33 which is, in turn, electrically connected to the movablecontact ll of the circuit breaker.

The electrical circuit through the breaker extends from the upperterminal conductor 9, through the stationary and movable contacts l3 andII, switch arm 3| which is of conducting material, through a portion ofthe releasable carrier lever 33, flexible conductor 8| and through thebimetallic strip St to the lower terminal conductor II. The bimetallicstrip 6| is thus heated in response to the current of the circuit and isarranged to deflect upwardly when heated a predetermined amount tooperate the latch member 51 to unlatched position to eflect tripping ofthe circuit breaker.

A motion amplifying means in the form of a cam lever 83 is provided foramplifying and transmittin the upward deflecting movement of the freeend of the bimetallic strip 9| to the outwardly extending lever arm ofthe latch lever 65. The cam lever 93 is of insulating material and ispivotally mounted by means of a pivot 95 supported in pivot recessesprovided in the casing 1 and side plate 23. The specific cam lever shownin the drawings is designed to amplify or multiply the deflectingmovement of the bimetallic strip 9| by two at the point where themovement is transmitted to the lever arm of the latch member 51. It willbe understood, of course, that more or less amplification of thedeflecting movement may be obtained by changing the shape and design ofthe cam lever 83. Deflecting movement of the bimetallic strip BI is thusmade'suflicient to move the latch portion 99 of the latch to releasedposition despite the fact that the latch surface is located close to theaxis of rotation of the latch, and yet the tripping force transmitted tothe latch is applied through a relatively long lever arm. Both themagnetic means 59 and the bimetallic trip element ll act on the latchmember through relatively long lever arms so that a large mechanicaladvantage is obtained and yet the entire trip mechanism occupies only asmall amount of space due to the novel arrangement of the parts. Withthis construction only a relatively light tripping force is required tooperate the latch to released position to effect tripping of thebreaker. The current, in flowing through the bimetallic element,energizes and produces the magnetic flux for. the magnetic trippingmeans so that no separate energizing coil or winding is required for themagnetic means.

The terminal conductor in is supported in a slot 81 provided therefor inthe casing i, and one end of this terminal conductor extends outwardlyinto a niche in thelower end of the casing and receives a terminal screwfor connecting this terminal of the breaker to the external circuit. Anadjusting screw 89 extends through the lower end of the casing l and isthreadedly engaged in an opening provided therefor in the inner portionof the terminal conductor H at a point remote from the supporting slot.The screw 89 thus serves as a means for adjusting the position of thebimetallic element 6!] to thereby adjust the thermal tripcharacteristicof the circuit breaker. Turning the screw 89 in one direction or theother changes the amount of deflection of the bimetallic strip 60 thatis necessary to effect tripping of the circuit breaker mechanism.

The operation of the trip device is as follows: when an overload belowthe instantaneous trip value occurs in the circuit controlled by thebreaker, the bimetallic element Si is heated by the overload current andwhen the element is heated a predetermined amount it deflects in anupward direction. The deflecting movement oi the bimetallic element 8!is amplified and transmitted by the cam lever 83 to one arm of the lever'65 causing counterclockwise movement of the latch member 51 position,therebydisengaging the latch portion I from the latch on the lower endof the releasable carrier lever 33. The carrier lever 33, when thusreleased, is actuated by' the spring 81 to.

cause automatic opening of the circuit breaker contacts in the mannerpreviously described. During the movement of the latch member 51 to itsreleased position the armature i is moved toward the pole faces of theU-shaped magnet 11, and, as the armature approaches the attractedposition, the pull of the magnet becomes stronger and assists in movingthe latch member 51 to released position. The electromagnet thus aidsthe bimetal in tripping the circuit breaker, and it will be apparentthat the aiding force of the magnetic means becomes stronger as themagnitude of the overload increases. This means that the circuit breakerwill be tripped more quickly as the magnitude of the overload increasesso that a faster tripping characteristic is obtained in the range ofmoderate to heavy overloads than would be provided by a bimetallic tripelement acting alone. I

Upon the occurrence of a heavy overload above the predeterminedmagnitude, for example, above eight to ten times normal rated current,and upon short circuits, the electromagnet is sufficiently energized toinstantaneously move the latch member 51 to released position before thebimetallic element 6| becomes substantially heated- In this instance thearmature "is quickly moved to attracted position, rotating the latch toreleased position independently of the. bimetal element 6 i. The carrierlever 33 is thusv instantaneously reabout its axis 68 to released leasedand causes automatic opening of the circuit breaker contacts.

With the construction shown, the magnetic tripping means does not exertany force on the bimetallic trip element at any time so that there is nodanger of overstressing the bimetallic trip element and damaging itscalibration.

It will be understood of course that the lever 86 of the latch mayitself be made of magnetic material and a magnetic rib corresponding tothe rib is secured to the inner lever arm of the magnetic lever 85 whichcooperates with the fixed magnet 11, or the whole lever and rib may beformed from a. single piece of magnetic material.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes inthe structural details and arrangement of parts may be made withoutdeparting from some of the essential features of the invention. It isdesired therefore that the language of the appended claims be given thebroadest reasonable interpretation permissible with the prior art.

I claim as my invention:

1. In a circuit breaker having relatively movable contacts, operatingmechanism therefor including a spring biased member releasable to causeautomatic opening operation of said contacts, a rotatably mounted latchmember for normally engaging and releasably restraining said releasablemember, said latch having a lever arm projecting therefrom, anelectromagnet for moving said latch to released position in response topredetermined overload conditions-comprising a magnetic armature membercarried by the lever arm of the latch, a cooperating magnetic membermounted adjacent the armature member, and an energizing conductorpassing between said magnetic members, one of said magnetic membersbeing U-shaped and the other having a projecting portion which at leastpartially extends into the space between the legs of the U-shaped memberin the normal unattracted position of the armature member. g

. 2. In a circuit breaker having relatively movable contacts, operatingmechanism therefor ineluding a spring biased member releasable to causeautomatic opening operation of said contacts, a latch for releasablyengaging and restraining said releasable member,' electromagnetic meansenergized in response to the current of the circuit for moving saidlatch to released position in response to predetermined overload currentconditions comprising a U-shaped member of magnetic material havingsubstantially'square ends on the legs of .the U forming magnetic polesurfaces, and an armature having spaced surfaces for attraction towardsaid pole surfaces and having a portion between said spaced surfacesprojecting at least partially into the space between the ends of the Uand providing a shorter air gap than between the square ends of the Uand said spaced surfaces when the armature is in its normal unattractedposition.

' 3. In a circuit breaker having relatively movable contacts, operatingmechanism therefor including a member releasable to cause automaticopening operation of said contacts, a rotatably mounted latch memberhaving a latch surface relatively close to the axis of rotation of saidlatch member for releasably engaging and restraining said releasablemember, a pair of lever:

arms projecting from said latch member, electroload current in thecircuit for moving said latch member to released position in response topredetermined overload conditions comprising a magnetizable armaturemember on one of said lever arms and a cooperative magnetizable membermounted adjacent said armature for attracting said armature, a bimetalelement heated in response to overload currents in the circuit operativeto deflect when heated a predetermined amount to move the other leverarm of said latch and thereby move said latch to released position, saidbimetal element having its free end disposed opposite said lastmentioned lever arm, and a pivoted motion amplifying member having anend extending between the free ends of said bimetal element and of saidlast-mentioned lever arm, said motion amplifying member engaging saidlast-mentioned lever arm at a point remote from the pivot of the motionamplifying member and being engaged by said bimetal element nearer tosaid pivot for amplifying and transmitting the deflecting movement ofthe free end of said bimetal element to said lever arm for actuatingsaid latch member.

4. In a circuit breaker having relatively movable contacts, operatingmechanism therefor including a member releasable to cause automaticopening operation of said contacts, a rotatably mounted latch member forreleasably engaging and normally restraining the releasable member, alever arm projecting from said latch member, a bimetal element heated inresponse to the current of the circuit and operative to defleet whenheated a predetermined amount by overload current to move said latchmember to released position and thereby release said releasable member,said bimetal element having its free end disposed opposite the free endof said lever arm, and a member pivoted adjacent one end at a fixedpoint and having its other end extending between said free ends of thebimetal element and the lever arm and engaged by the bimetal elementnear the pivot of the member and having its end remote from its pivotengaging said lever arm for amplifying and transmitting the deflectingmovement of the free end of said bimetal element to said lever arm.

5. A circuit breaker having relatively movable contacts, operatingmechanism therefor including a member releasable to cause automaticopeningoperation of said contacts, a rotatably mounted latch memberhaving a latch surface relatively close to the axis of rotation of thelatch member for releasably engaging and normally restraining saidreleasable member, a lever arm projecting beyond said latch, a bimetalelement connected in circuit with said contacts and operative to deflectwhen heated a predetermined amount by overload currents to move saidlatch member toward released position, said bimetal element having itsfree end disposed adjacent the free end of the lever arm, and a lever ofinsulating material having a fixed pivot for amplifying and transmittingthe deflecting movement of the free end of said bimetal element to saidlever arm of the latch, said lever of insulating material having an endwhich separably engages the projecting latch lever arm, and the free endof said bimetal element separably engaging said lever of insulatingmaterial at a point closer to the pivot axis of the lever of insulatingmaterial than the end thereof.

6. In a circuit breaker having relatively movable contacts, operatingmechanism therefor including a member releasable to cause automaticopening operation of said contacts, a rotatably mounted latch memberhaving a latch surface close to the axis of rotation of said latchmember for releasably engaging and restraining said releasable member, apair of lever arms projecting from said latchmember, electromagneticmeans energized in response to overload current in the circuit formoving said latch member to released position in response topredetermined overload conditions comprising a magnetizable armaturemember mounted on one of said lever arms and a cooperating magnetizablemember mounted adjacent said armature for attracting said armature, oneof said magnetizable members being U-shaped and the other having aprojection which at least partially extends into the space between thelegs of the U-shaped member, a bimetal element heated in response to theoverload currents in the circuit and operative to deflect and move theother lever arm of said latch and thereby move said latch towardreleased position and at the same time shorten the air gap between saidarmature member and said magnetizable member, and a pivoted lever ofinsulating material for amplifying and transmitting the heat deflectingmovement of said bimetal element to said other lever arm of the latch,said latch being movable to released position by said electromagneticmeans independently of said bimetal element and without moving saidbimetal'element.

OLIVER s. JENNINGS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 535,069 McElroy et al Mar. 5,1895 570,419 Wurts Oct. 27, 1896 677,353 Hewlett July 2, 1901 689,836Wheeler Dec. 24, 1901 2,027,238 Lindstrom Jan. 7, 1936 2,035,743 Franket al Mar. 31, 1936 2,043,306 Sandin June 9, 1936 2,046,701 Sanden July7, 1936 2,048,114 Gano et a1. July 21, 1936 2,353,756 Price July 18,1944 FOREIGN PATENTS Number Country Date 95,895 Sweden June 6, 1939

